Observational studies of Cepheid amplitudes. II Metallicity dependence of pulsation amplitudes

Abstract

Physical and phenomenological properties (radius, luminosity, shape of the light curve, etc.) of Cepheids strongly depend on the pulsation period, with the exception of the pulsation amplitude. A possible factor causing a wide range of pulsation amplitudes might be the different atmospheric metallicities of individual Cepheids. We studied the influence exerted by the atmospheric iron content, [Fe/H], on the pulsational amplitude of Galactic Cepheids. We searched for correlations between the [Fe/H] value and both the observed amplitudes and amplitude related parameters. The amplitude of the Cepheid pulsation slightly decreases with increasing iron abundance. This effect is more pronounced for the radial velocity variations and for the shorter pulsation periods. The wavelength dependence of photometric amplitudes is also found to be sensitive to the metallicity. Some of these effects are not consequences of differential line blanketing. Based on the calibrations of the metallicity sensitivity relationships, we derived photometric iron abundance for 21 Galactic Cepheids. The dichotomic behaviour dividing Galactic Cepheids that pulsate in the fundamental mode into short- and long-period groups at the period of 10.47 d can be noticed in some diagrams that show metallicity-related dependences. We confirm that variety in atmospheric metallicity in Cepheids contributes to the finite range of pulsation amplitudes at a given period. Effects of metallicity on the amplitudes revealed from observational data and the occurrence of the dichotomy also derived from phenomenological data have to be confirmed by appropriate theoretical models of stellar structure and pulsation.

9 pages, 8 figures, accepted for publication in the Astronomy and Astrophysics

References in corpus (3)

• The Distribution of the Elements in the Galactic Disk III. A Reconsideration of Cepheids from l = 30 to 250 Degrees
• The influence of chemical composition on the properties of Cepheid stars. II-The iron content
• Study of the effect of metallicity on the amplitudes of Cepheids

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• TESS observations of Cepheid stars: first light results
• A Global Physical Model for Cepheids
• The Metallicity Dependence of the Cepheid P-L Relation in M101
• Determination of the iron content of Cepheids from the shape of their light curves
• Problems and possibilities in fine-tuning of the Cepheid P-L relationship
• On the Metallicity Dependence of Classical Cepheid Light Amplitudes
• Metallicity estimation of MW, SMC and LMC classical Cepheids from the shape of the $V$- and $I$-band light curves
• Precise Fourier parameters of Cepheid Radial Velocity Curves
• Evidence for Photometric Contamination in Key Observations of Cepheids in the Benchmark Galaxy IC 1613
• Dependence of pulsation mode of Cepheids on metallicity
• Reconstruction of Cepheid Radial Velocity Curves from the shape of the V-band Light Curves